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1.
Trust-region based instantaneous optimal semi-active control of long-span spatially extended structures with MRF-04K damper 总被引：1，自引：0，他引：1
In the field of civil engineering, magnetorheological fluid （MRF） damper-based semi-active control systems have received considerable attention for use in protecting structures from natural hazards such as strong earthquakes and high winds. In this paper, the MRF damper-based semi-active control system is applied to a long-span spatially extended structure and its feasibility is discussed. Meanwhile, a _trust-region method based instantaneous optimal semi-active control algorithm （TIOC） is proposed to improve the performance of the semi-active control system in a multiple damper situation. The proposed TIOC describes the control process as a bounded constraint optimization problem, in which an optimal semi- active control force vector is solved by the trust-region method in every control step to minimize the structural responses. A numerical example of a railway station roof structure installed with MRF-04K dampers is presented. First, a modified Bouc- Wen model is utilized to describe the behavior of the selected MRF-04K damper. Then, two semi-active control systems, including the well-known clipped-optimal controller and the proposed TIOC controller, are considered. Based on the characteristics of the long-span spatially extended structure, the performance of the control system is evaluated under uniform earthquake excitation and travelling-wave excitation with different apparent velocities. The simulation results indicate that the MR fluid damper-based semi-active control systems have the potential to mitigate the responses of full-scale long-span spatially extended structures under earthquake hazards. The superiority of the proposed TIOC controller is demonstrated by comparing its control effectiveness with the clipped-optimal controller for several different cases. 相似文献
2.
The electromagnetic mass damper （EMD） control system, as an innovative active control system to reduce structural vibration, offers many advantages over traditional active mass driver/damper （AMD） control systems. In this paper, studies of several EMD control strategies and bench-scale shaking table tests of a two-story model structure are described. First, two structural models corresponding to uncontrolled and Zeroed cases are developed, and parameters of these models are validated through sinusoidal sweep tests to provide a basis for establishing an accurate mathematical model for further studies. Then, a simplified control strategy for the EMD system based on the pole assignment control algorithm is proposed. Moreover, ideal pole locations are derived and validated through a series of shaking table tests. Finally, three benchmark earthquake ground motions and sinusoidal sweep waves are imposed onto the structure to investigate the effectiveness and feasibility of using this type of innovative active control system for structural vibration control. In addition, the robustness of the EMD system is examined. The test results show that the EMD system is an effective and robust system for the control of structural vibrations. 相似文献
3.
This paper presents an experimental investigation on semi-active seismic response control of a multistory building with a podium structure using multiple magnetorheological (MR) dampers manipulated by a logic control algorithm. The experiments are performed in three phases on a seismic simulator with a slender 12-story building model representing a multi-story building and a relatively stiff 3-story building model typifying a podium structure. The first phase of the investigation is to assess control performance of using three MR dampers to link the 3-story building to the 12-story building, in which seismic responses of the controlled two buildings are compared with those of the two buildings without any connection and with rigid connection. The second phase is to investigate reliability of the semi-active control system and robustness of the logic control algorithm when 2 out of 3 MR dampers fail and when the electricity supply to MR dampers is completely stopped. The last phase is to examine sensitivity of semi-active control performance of two buildings to change in ground excitation. The experimental results show that multiple MR dampers with the logic control algorithm can achieve a significant reduction in seismic responses of both buildings. The proposed semi-active control system is of high reliability and good robustness. 相似文献
4.
This paper presents a procedure to develop fragility curves of structures equipped with TMD considering multiple failure functions.The failure criteria considered are maximum inter-story drift ratio as a safety criterion,maximum absolute acceleration as a convenience criterion and TMD stroke length.The relationship between intensity measure and responses of the structure was assumed to follow the power-law model,and a regression analysis was used to estimate its properties.A nonlinear eight-story shear building subjected to near-fault earthquakes was used for the numerical studies.Fragility curves using multiple and single failure functions for an uncontrolled structure and a structure equipped with optimal TMDs were developed.Numerical analysis showed that using multiple failure functions led to increasing the fragility when compared with using the single failure function for both the uncontrolled and controlled structures.However,TMDs slightly reduced the seismic fragility and have the capability to improve the reliability of the structure.Also,it was found that the fragility was significantly influenced by the values of the capacity thresholds of both the acceleration of the structure and TMD stroke length,which should be selected by considering the target performance and application of the structure and control device. 相似文献
5.
To avoid soil erosion, lters often are installed in the downstream cross section of dams. However, the probability of piping failure and the lter effect both are related to the soil pore network. Previous erosion probability models for a base soil- lter system do not consider the effect of local ow. Therefore, in this study, an improved erosion probability model is established, in which the deviation between the main ow direction of the soil and the local ow direction in the lter was considered based on a previous model. The improved model was validated by numerical simulation. The erosion probability was found to affect the reasonable evaluation of lter effects and the optimal selection of lter thickness. The controlling con- striction size in a granular lter was increased to Dc* Dc5 with a lter thickness of 59 Dm. 相似文献
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The problem of robust active vibration control for a class of electro-hydraulic actuated structural systems with time-delay in the control input channel and parameter uncertainties appearing in all the mass,damping and stiffness matrices is investigated in this paper.First,by introducing a linear varying parameter,the nonlinear system is described as a linear parameter varying(LPV)model.Second,based on this LPV model,an LMI-based condition for the system to be asymptotically stabilized is deduced.By solving these LMIs,a parameter-dependent controller is established for the closedloop system to be stable with a prescribed level of disturbance attenuation.The condition is also extended to the uncertain case.Finally,some numerical simulations demonstrate the satisfying performance of the proposed controller. 相似文献
8.
RIV1H is the stand-alone hydraulic program of CE-QUAL-RIV1, a longitudinal hydraulic and water quality model developed by U.S. Army Corps of Engineers Waterways Experiment Station. RIV1H solves the Saint-Venant equations using the widely accepted four-point implicit Preissmann scheme, and the resulting nonlinear equations are solved using the Newton-Raphson method. RIV1H is capable of simulating multiple branches, and in-stream hydraulic control structures. It treats tributary networks using a double sweep algorithm based on upstream ordering of the branches. It treats the control structures following a downstream solution order, which also is based on the upstream ordering of the branches. Since an upstream ordering cannot be achieved for looped networks, RIV1H is only applicable to non-looped tributary networks. In the current study, the junction-point water stage prediction and correction (JPWSPC) method is extended to take into account the control structures and the method is used to improve the RIV1H model, enabling it to be applied to both non-looped and looped networks with in-stream hydraulic control structures. The JPWSPC method makes the linear equation system for each segment complete while maintaining the banded property, thus the system can be independently and efficiently solved. It has the advantages to be efficient, robust, and very suitable for parallel computing. The improved RIV1H model was tested using two idealized networks and the results demonstrated the success of the improvement. 相似文献
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10.
Yongping YUAN Ronald BINGNER Randall WILLIAMS Richard LOWRANCE David BOSCH Joe SHERIDAN 《国际泥沙研究》2007,22(1):60-69
The United States Department of Agriculture (USDA) Annualized Agricultural Non-Point Source Pollution model (AnnAGNPS) is used to help evaluate a watershed response to agricultural management practices to control water quality. However, AnnAGNPS version 3.5 does not contain features to estimate the effect of a riparian buffer (RB) system on water quality. The Riparian Ecosystem Management Model (REMM) is used to simulate the impact of riparian buffer systems on water quality. However, frequently the lack of measured upland loadings that are required by REMM simulation limits the application of REMM. To address this data gap, a study was conducted to integrate AnnAGNPS with REMM for RB system simulation. AnnAGNPS was used to simulate water and sediment loadings from an upland field into a three-zone RB system at the Gibbs Farm located in the Georgia coastal plain. These AnnAGNPS outputs were used as the inputs to REMM. REMM was used to simulate water and sediment movement along the riparian buffers. The AnnAGNPS simulated amount of annual runoff at the edge of the field was close to observed amounts (Nash-Sutcliffe efficiency of 0.92). It is believed that a substantial portion of sand was removed from the runoff one meter into the grass buffer where the samplers were located; therefore, sand was excluded from the AnnAGNPS simulation for comparison with observed sediment. Excluding sand, the AnnAGNPS predicted amount of annual sediment matches the observed amount fairly well (Nash-Sutcliffe efficiency of 0.46). In addition, based on evaluating the percent reduction of sediment at each zonal interface, the AnnAGNPS/REMM model well simulated the function of the RB system to reduce sediment. 相似文献
11.
In the current state of geomagnetic instrument testing, some aspects of geomagnetic instrument performance are difficult to test in the laboratory. If laboratory test results are inadequate, the instrument will have multiple problems while operating in the field, where a geomagnetic instrumentation test platform with a stable natural magnetic field is critical. Here, the magnetic field feedback circuit for geomagnetic field compensation control is studied in detail. That is, the magnetic field measured by the feedback magnetic sensor and the required working magnetic field are compared as input to the system, and the electric signal is transmitted to the feedback coil through an analog circuit to form a closed loop control, which provides compensation to control the magnetic field. Compared with the existing magnetic shielding method, the analog control circuit can achieve the realization of any working magnetic field, and it is not limited to a null magnetic field. The experimental result shows that the system compensates the earth''s magnetic field of 10,000nT with an average error of 10.6nT and average compensation error of 0.106%, providing a high compensation accuracy. The system also shows high sensitivity and excellent stability. The feedback circuit has achieved effective compensation control for the earth''s magnetic field. 相似文献
12.
China has developed an airborne gravimetry system based on SINS/DGPS named SGA-WZ,the first system in which a strapdown inertial navigation system(SINS)has been used for airborne gravimetry in China.This gravity measurement system consists of a strap-down inertial navigation system and a differential global positioning system(DGPS).In April 2010,a flight test was carried out in Shandong Province of China to test the accuracy of this system.The test was designed to assess the repeatability and accuracy of the system.Two repeated flights and six grid flights were made.The flying altitude was about 400 m.The average flying speed was about 60 m/s,which corresponds to a spatial resolution of 4.8 km when using 160-s cutoff low-pass filter.This paper describes the data processing of the system.The evaluation of the internal precision is based on repeated flights and differences in crossover points.Gravity results in this test from the repeated flight lines show that the repeatability of the repeat lines is 1.6 mGal with a spatial resolution of 4.8 km,and the internal precision of grid flight data is3.2 mGal with a spatial resolution of 4.8 km.There are some systematic errors in the gravity results,which can be modeled using trigonometric function.After the systematic errors are compensated,the precision of grid flight data can be better than1 mGal. 相似文献
13.
A building retrofitted with wing walls in the bottom story, which was damaged during the 2008 M8.0 Wenchuan earthquake in China, is introduced and a corresponding 1/4 scale wing wall-frame model was subjected to shake table motions to study the seismic behavior of this retrofitted structural system. The results show that wing walls can effectively protect columns from damage by moving areas that bear reciprocating tension and compression to the sections of the wing walls, thus achieving an extra measure of seismic fortification. A ‘strong column-weak beam' mechanism was realized, the flexural rigidity of the vertical member was strengthened, and a more uniform distribution of deformation among all the stories was measured. In addition, the joint between the wing walls and the beams suffered severe damage during the tests, due to an area of local stress concentration. A longer area of intensive stirrup is suggested in the end of the beams. 相似文献
14.
A hybrid control platform is investigated in this paper to mitigate microvibrations to a group of vibration-sensitive equipment installed in a microelectronics facility subject to nearby road vehicle-induced horizontal and vertical ground motions. The hybrid control platform, on which microelectronics equipment is installed, is mounted on a building floor through a series of passive mounts and controlled by hydraulic actuators in both horizontal and vertical directions. The control platform is an elastic body with significant bending modes of vibration, and a sub-optimal control algorithm is used to manipulate the hydraulic actuators with actuator dynamics included. The finite element model and the equations of motion of the coupled platform-building system are then established in the absolute coordinate to facilitate the feedback control and performance evaluation of the platform. The horizontal and vertical ground vibrations at the base of the building induced by nearby moving road vehicles are assumed to be stationary random processes. A typical three-story microelectronics building is selected as a case study. The case study shows that the vertical vibration of the microelectronics building is higher than the horizontal. The use of a hybrid control platform can effectively reduce both horizontal and vertical microvibrations of the microelectronics equipment to the level which satisfies the stringent microscale velocity requirement specified in the Bolt Beranek & Newman (BBN) criteria. 相似文献
15.
The objective of this research is to determine the effect earthquakes have on the performance of transportation network systems. To do this, bridge fragility curves, expressed as a function of peak ground acceleration (PGA) and peak ground velocity (PGV), were developed. Network damage was evaluated under the 1994 Northridge earthquake and scenario earthquakes. A probabilistic model was developed to determine the effect of repair of bridge damage on the improvement of the network performance as days passed after the event. As an example, the system performance degradation measured in terms of an index, “Drivers Delay,“ is calculated for the Los Angeles area transportation system, and losses due to Drivers Delay with and without retrofit were estimated. 相似文献
16.
It is a challenge to make thorough but efficient experimental designs for the coupled mineral dissolution and precipitation studies in a multi-mineral system, because it is difficult to speculate the best experimental duration, optimal sampling schedule, effects of different experimental conditions, and how to maximize the experimental outputs prior to the actual experiments. Geochemical modeling is an efficient and effective tool to assist the experimental design by virtually running all scenar... 相似文献
17.
The success of the tuned mass damper (TMD) in reducing wind-induced structural vibrations has been well established. However, from most of the recent numerical studies, it appears that for a structure situated on very soft soil, soilstructure interaction (SSI) could render a damper on the structure totally ineffective. In order to experimentally verify theSSI effect on the seismic performance ofTMD, a series of shaking table model tests have been conducted and the results are presented in this paper. It has been shown that the TMD is not as effective in controlling the seismic responses of structures built on soft soil sites due to the SSI effect. Some test results also show that a TMD device might have a negative impact if the SSI effect is neglected and the structure is built on a soft soil site. For structures constructed on a soil foundation, this research verifies that the SSI effect must be carefully understood before a TMD control system is designed to determine if the control is necessary and if the SSI effect must be considered when choosing the optimal parameters of the TMD device. 相似文献
18.
The optimal matrix method and optimal elemental method used to update finite element models may not provide accurate results. This situation occurs when the test modal model is incomplete, as is often the case in practice. An improved optimal elemental method is presented that defines a new objective function, and as a byproduct, circumvents the need for mass normalized modal shapes, which are also not readily available in practice. To solve the group of nonlinear equations created by the improved optimal method, the Lagrange multiplier method and Matlab function fmincon are employed. To deal with actual complex structures, the float-encoding genetic algorithm (FGA) is introduced to enhance the capability of the improved method. Two examples, a 7degree of freedom (DOF) mass-spring system and a 53-DOF planar frame, respectively, are updated using the improved method.The example results demonstrate the advantages of the improved method over existing optimal methods, and show that the genetic algorithm is an effective way to update the models used for actual complex structures. 相似文献
19.
The Bayesian probabilistic approach is proposed to estimate the process noise and measurement noise parameters for a Kalman filter. With state vectors and covariance matrices estimated by the Kalman filter, the likehood of the measurements can be constructed as a function of the process noise and measurement noise parameters. By maximizing the likelihood function with respect to these noise parameters, the optimal values can be obtained. Furthermore, the Bayesian probabilistic approach allows the associated uncertainty to be quantified. Examples using a single-degree-of-freedom system and a ten-story building illustrate the proposed method. The effect on the performance of the Kalman filter due to the selection of the process noise and measurement noise parameters was demonstrated. The optimal values of the noise parameters were found to be close to the actual values in the sense that the actual parameters were in the region with significant probability density. Through these examples, the Bayesian approach was shown to have the capability to provide accurate estimates of the noise parameters of the Kalman filter, and hence for state estimation. 相似文献
20.
Base isolated structures have been found to be at risk in near-fault regions as a result of long period pulses that may exist in near-source ground motions.Various control strategies,including passive,active and semi-active control systems,have been investigated to overcome this problem.This study focuses on the development of a semi-active control algorithm based on several performance levels anticipated from an isolated building during different levels of ground shaking corresponding to various earthquake hazard levels.The proposed performance-based algorithm is based on a modified version of the well-known semi-active skyhook control algorithm.The proposed control algorithm changes the control gain depending on the level of shaking imposed on the structure.The proposed control system has been evaluated using a series of analyses performed on a base isolated benchmark building subjected to seven pairs of scaled ground motion records.Simulation results show that the newly proposed algorithm is effective in improving the structural and nonstructural performance of the building for selected earthquakes. 相似文献